Chiral acyclic diaminocarbene ligands, precursors therefore and their use in organic synthesis reactions

ABSTRACT

The current application relates to a metal catalyst of formula (I): M[ADC][X] n , wherein M is a metal, ADC is a chiral acyclic diaminocarbene ligand, and X is a neutral or anionic ligand. The ADC ligand is prepared from the corresponding chiral formamidium salt precursor. The metal catalyst is used for asymmetric organic synthesis reactions such as hydrosilations, hydrogenations, conjugate additions, and cross-couplings.

FIELD OF THE DISCLOSURE

The present disclosure is in the field of metal catalysts for organicsynthesis reactions, in particular to metal catalysts comprising achiral acyclic diamino carbene ligand.

BACKGROUND OF THE DISCLOSURE

It is established that enantiomers can possess unique activities wheninteracting with chiral biological systems (e.g. enzymes).^(1a) As aconsequence, the pharmaceutical industry has migrated to manufacturingand marketing single enantiomeric forms of chiral drugs (e.g. 80% ofsmall-molecule drugs approved by the FDA in 2006 were chiral and 75%were single enantiomers).^(1a) The growing economic importance ofsingle-enantiomer production has led to significant expansion ofresearch into chiral synthesis.^(1b)

The catalysis approach towards asymmetric synthesis offers severaldistinct advantages (e.g. cost savings, less waste generation) over moretraditional protocols such as chiral stoichiometric reagents and chiralauxiliaries. In particular, transition metal (TM) catalysis hasrevolutionized organic synthesis.² The near constant improvement in thefield of TM catalysis is undoubtedly due in large part to theintroduction of new and improved ligands, which allows for desiredtransformations to be carried out in a more efficient manner (i.e.milder conditions, lower catalyst loadings, higher yields and higherenantioselectivities when applicable).

Recently, N-heterocyclic carbenes (NHC) have had a significant impact inthe field of achiral TM catalysis. NHC (e.g. 1-3) have proven themselvesto be viable, and in many cases, superior ligands to the moretraditional phosphorus based ligands.³

The improved characteristics of NHC flow from the fact that they aresuperior two electron donors to the TM centre.⁴ Unfortunately, however,there are only a handful of TM-catalyzed transformations employingchiral NHC ligands that have afforded products with highenantioselectivities.⁵ As a result, chiral phosphorus-based ligandscontinue to dominate the field of enantioselective catalysis.^(1b)

Unlike NHC, acyclic diamino carbenes (ADC)⁶ (4) have attracted scantattention from the synthetic community.⁷

Certain achiral ADC have been examined in TM catalyzed cross-couplingreactions.⁸ It was demonstrated that ADC are effective ligands for threeimportant cross-couplings reactions viz Suzuki, Sonogashira and Heckreactions.⁸

SUMMARY OF THE DISCLOSURE

A new array of chiral ADC ligands that have been employed inenantioselective catalysis has been developed. A variety of symmetricand non-symmetric chiral acyclic formamidium salts have been prepared asprecursors to their corresponding diamino carbenes. Various metalcatalysts having these chiral ADC's as ligands have also been preparedand used in metal-catalyzed organic synthesis transformations.

Accordingly, the present disclosure includes a metal catalyst of theformula I:

M[ADC][X]_(n)  (I)

whereinM is a metal;ADC is a chiral acyclic carbene of the formula II:

R¹, R², R³ and R⁴ are independently selected from C₁₋₁₀alkyl,C₂₋₁₀alkenyl, C₂₋₁₀alkynyl, C₃₋₁₀cycloalkyl, heteroaryl and aryl, eachgroup being optionally substituted, orR¹ and R² are linked to form, together with the nitrogen atom to whichthey are attached, an optionally substituted monocyclic or polycyclic,saturated or unsaturated ring system that contains 3 to 30 carbon atoms,of which one or more of the carbon atoms is optionally replaced with aheteromoiety selected from O, S, NH and NC₁₋₆alkyl, and/orR³ and R⁴ are linked to form, together with the nitrogen atom to whichthey are attached, an optionally substituted monocyclic or polycyclic,saturated or unsaturated ring system that contains 3 to 30 carbon atoms,of which one or more of the carbon atoms is optionally replaced with aheteromoiety selected from O, S, NH and NC₁₋₆alkyl,the optional substituents on R¹, R², R³ and R⁴ are independentlyselected from one or more of C₁₋₆alkyl, halo, halo-substitutedC₁₋₆alkyl, C₃₋₁₀cycloalkyl, aryl and heteroaryl, and

at least one of R¹, R², R³, R⁴, the ring system formed by R¹ and R² andthe ring system formed by R³ and R⁴, or a substituent thereon, comprisesat least one chiral center;

X is a neutral or an anionic ligand; andn is an integer representing the number of ligands, X, to fulfill thevalency requirements of N, and when x is greater than 1, each X may bethe same or different.

Accordingly, the present disclosure includes a chiral formamidium saltof the formula III:

whereinR¹, R², R³ and R⁴ are independently selected from C₁₋₁₀alkyl,C₂₋₁₀alkenyl, C₂₋₁₀alkynyl, C₃₋₁₀cycloalkyl, heteroaryl and aryl, eachgroup being optionally substituted, orR¹ and R² are linked to form, together with the nitrogen atom to whichthey are attached, an optionally substituted monocyclic or polycyclic,saturated or unsaturated ring system that contains 3 to 30 carbon atoms,of which one or more of the carbon atoms is optionally replaced with aheteromoiety selected from O, S, NH and NC₁₋₆alkyl, and/orR³ and R⁴ are linked to form, together with the nitrogen atom to whichthey are attached, an optionally substituted monocyclic or polycyclic,saturated or unsaturated ring system that contains 3 to 30 carbon atoms,of which one or more of the carbon atoms is optionally replaced with aheteromoiety selected from O, S, NH and NC₁₋₆alkyl,the optional substituents on R¹, R², R³ and R⁴ are independentlyselected from one or more of C₁₋₆alkyl, halo, halo-substitutedC₁₋₆alkyl, C₃₋₁₀cycloalkyl, aryl and heteroaryl, andat least one of R¹, R², R³, R⁴, the ring system formed by R¹ and R² andthe ring system formed by R³ and R⁴, or a substituent thereon, comprisesat least one chiral center; andY is a non-coordinating counter anion.

The present disclosure also includes a method of performingmetal-catalyzed organic synthesis reactions comprising contactingsubstrates for the organic synthesis reaction with a metal catalyst ofthe formula I as defined above under conditions for performing theorganic synthesis reaction, and optionally isolating one or moreproducts from the organic synthesis reaction. In an embodiment of thedisclosure, the organic synthesis reaction is any reaction that benefitsfrom the presence or use of a metal catalyst, for example, but notlimited to, hydrosilations, hydrogenations, conjugate additions andcross-couplings. In an embodiment of the disclosure, the organicsynthesis transformation is an asymmetric or chiral synthesis reaction(i.e. provides one enantiomer in excess of the other).

Other features and advantages of the present disclosure will becomeapparent from the following detailed description. It should beunderstood, however, that the detailed description and the specificexamples while indicating preferred embodiments of the disclosure aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the disclosure will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will now be described in greater detail withreference to the attached drawings in which:

FIG. 1 is an X-ray crystal structure of(2R,5R)-1-(((2R,5R)-2,5-diphenylpyrrolidin-1-yl)methylene)-2,5-diphenylpyrrolidiniumiodide (compound IIIj; Y═I⁻).

DETAILED DESCRIPTION OF THE DISCLOSURE (I) Definitions

The term “C_(1-n)alkyl” as used herein means straight and/or branchedchain, saturated alkyl groups containing from one to “n” carbon atomsand includes (depending on the identity of n) methyl, ethyl, propyl,isopropyl, n-butyl, s-butyl, isobutyl, t-butyl, 2,2-dimethylbutyl,n-pentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, n-hexyl andthe like, where the variable n is an integer representing the largestnumber of carbon atoms in the alkyl group.

The term “C_(1-n)alkenyl” as used herein means straight and/or branchedchain, unsaturated alkyl groups containing from one to n carbon atomsand one to three double bonds, and includes (depending on the identityof n) vinyl, allyl, 2-methylprop-1-enyl, but-1-enyl, but-2-enyl,but-3-enyl, 2-methylbut-1-enyl, 2-methyl-pent-1-enyl,4-methylpent-1-enyl, 4-methylpent-2-enyl, 2-methylpent-2-enyl,4-methylpenta-1,3-dienyl, hexen-1-yl and the like, where the variable nis an integer representing the largest number of carbon atoms in thealkenyl group.

The term “C_(1-n)alkynyl” as used herein means straight and/or branchedchain, unsaturated alkyl groups containing from one to n carbon atomsand one to three three bonds, and includes (depending on the identity ofn) propargyl, 2-methylprop-1-ynyl, but-1-ynyl, but-2-ynyl, but-3-ynyl,2-methylbut-1-ynyl, 2-methylpent-1-ynyl, 4-methylpent-1-ynyl,4-methylpent-2-ynyl, 2-methylpent-2-ynyl, 4-methylpenta-1,3-diynyl,hexyn-1-yl and the like, where the variable n is an integer representingthe largest number of carbon atoms in the alkynyl group.

The term “C_(3-n)cycloalkyl” as used herein means a monocyclic, bicyclicor tricyclic saturated carbocylic group containing from three to ncarbon atoms and includes (depending on the identity of n) cyclopropyl,cyclobutyl, cyclopentyl, cyclodecyl and the like, where the variable nis an integer representing the largest number of carbon atoms in thecycloalkyl group.

The term “aryl” as used herein means a monocyclic, bicyclic or tricyclicaromatic ring system containing from 6 to 14 carbon atoms and at leastone aromatic ring and includes phenyl, naphthyl, anthracenyl,1,2-dihydronaphthyl, 1,2,3,4-tetrahydronaphthyl, fluorenyl, indanyl,indenyl and the like.

The term “heteroaryl” as used herein means a monocyclic, bicyclic ortricyclic ring system containing one or two aromatic rings and from 5 to14 atoms of which, unless otherwise specified, one, two, three, four orfive are heteroatoms independently selected from N, NH, N(C₁₋₆alkyl), Oand S and includes thienyl, furyl, pyrrolyl, pyrididyl, indolyl,quinolyl, isoquinolyl, tetrahydroquinolyl, benzofuryl, benzothienyl andthe like.

The term “halo” as used herein means halogen and includes chloro,fluoro, bromo and iodo.

The term “ring system” as used herein refers to a carbon-containing ringsystem, that includes monocycles, fused bicyclic and polycyclic ringsand bridged rings. Where specified, the carbons in the rings may besubstituted or replaced with heteroatoms.

In understanding the scope of the present disclosure, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. Finally, terms of degree such as “substantially”, “about”and “approximately” as used herein mean a reasonable amount of deviationof the modified term such that the end result is not significantlychanged. These terms of degree should be construed as including adeviation of at least ±5% of the modified term if this deviation wouldnot negate the meaning of the word it modifies.

(II) Catalysts and Ligands

The present disclosure includes a metal catalyst of the formula I:

M[ADC][X]_(n)  (I)

whereinM is a metal;ADC is a chiral acyclic carbene of the formula II:

R¹, R², R³ and R⁴ are independently selected from C₁₋₁₀alkyl,C₂₋₁₀alkenyl, C₂₋₁₀alkynyl, C₃₋₁₀cycloalkyl, heteroaryl and aryl, eachgroup being optionally substituted, orR¹ and R² are linked to form, together with the nitrogen atom to whichthey are attached, an optionally substituted monocyclic or polycyclic,saturated or unsaturated ring system that contains 3 to 30 carbon atoms,of which one or more of the carbon atoms is optionally replaced with aheteromoiety selected from O, S, NH and NC₁₋₆alkyl, and/orR³ and R⁴ are linked to form, together with the nitrogen atom to whichthey are attached, an optionally substituted monocyclic or polycyclic,saturated or unsaturated ring system that contains 3 to 30 carbon atoms,of which one or more of the carbon atoms is optionally replaced with aheteromoiety selected from O, S, NH and NC₁₋₆alkyl,the optional substituents on R¹, R², R³ and R⁴ are independentlyselected from one or more, optionally one to five, suitably one tothree, of C₁₋₆alkyl, halo, halo-substituted C₁₋₆alkyl, C₃₋₁₀cycloalkyl,aryl and heteroaryl, andat least one of R¹, R², R³, R⁴, the ring system formed by R¹ and R² andthe ring system formed by R³ and R⁴, or a substituent thereon, comprisesat least one chiral center;X is a neutral or an anionic ligand; andn is an integer representing the number of ligands, X, to fulfill thevalency requirements of N, and when x is greater than 1, each X may bethe same or different.

In an embodiment of the disclosure R¹, R², R³ and R⁴ in the ADC's offormula II are independently selected from C₁₋₆alkyl, C₅₋₆cycloalkyl andaryl, each group being optionally substituted, or R¹ and R² and/or R³and R⁴ are linked to form, together with the nitrogen atom to which theyare attached, an optionally substituted monocyclic, saturated ringsystem that contains 4 to 7 carbon atoms, and the optional substituentson R¹, R², R³ and R⁴ are independently selected from one or more,optionally one to five, suitably one to three, of C₁₋₄alkyl,halo-substituted C₁₋₄alkyl, C₅₋₆cycloalkyl and aryl, and at least one ofR¹, R², R³, R⁴, the ring system formed by R¹ and R² and the ring systemformed by R³ and R⁴, or a substituent thereon, comprises at least onechiral center.

In a further embodiment of the disclosure, ADC of formula II is selectedfrom:

and analogs of the above compounds that are substituted on the alkylgroups, phenyl rings, aromatic and/or pyrrolidine rings with one or moresubstituents independently selected from C₁₋₆alkyl, halo,halo-substituted C₁₋₆alkyl, OC₁₋₆alkyl and halo-substituted OC₁₋₆alkyl.

The metal M may be any metal used in catalysts for metal-catalyzedorganic synthesis reactions. In an embodiment of the invention, themetal is any transition metal, or other metal selected from B, Al, Ga,Ge, In, Sn, Sb, Ti, Pb, Bi and Po, or a lanthanide or actinide. Examplesof suitable metals include, but are not limited to Cu, Ag, Au, Sn, Ni,Pd, Pt, Co, Rh, Ir, Fe, Ru, Os and Re.

In an embodiment of the disclosure, X is selected from any ancillaryligand, including phosphine, amine, alkene, diamine, diphosphine,aminophosphine, halo (for example, fluoro, chloro, bromo or iodo,specifically chloro), HO⁻, R⁵O⁻ and R⁵C(O)O⁻, wherein R⁵ is H orC₁₋₆alkyl. In an embodiment of the disclosure, X is chloro. When n isgreater than 1, it is an embodiment of the disclosure that all X ligandsare the same. X may also be a multidentate ligand.

A person skilled in the art would appreciate that n is an integer thatwill depend on the identity and oxidation state of M and the identity ofX.

The preparation of the catalysts of formula I is suitably done bygenerating the ADC ligand in situ from a formamidium salt of formulaIII, followed by addition of an appropriate metal precursor complex orsalt:

whereinR¹, R², R³ and R⁴ are as defined in formula II and Y is anon-coordinating counter anion. Suitably the ADC of formula II isgenerated from a formamidium salt of formula III by reaction with astrong base, such as an alkyl lithium or lithium amide, at reducedtemperatures, for example at −50° C. to about −90° C. The resultingreaction mixture is then reacted for a time and at a temperaturesufficient for the formation of the ADC of formula II (determinable by aperson skilled in the art), then the appropriate metal compound isadded, suitably at reduced temperatures, for example at −50° C. to about−90° C., to form the catalysts of formula I. A person skilled in the artwould appreciate that the reaction times and temperatures can be varied,depending on the identity of the compounds of formula II and metalprecursor compound, to optimize the yield of the catalysts of formula I.The catalysts of formula I, so prepared, may be used without isolationin any organic synthesis transformation.

The present disclosure further includes a formamidium salt useful as aprecursor to the chiral ADC's of the present disclosure. Accordingly,the present disclosure includes a chiral formamidium salt of the formulaIII:

whereinR¹, R², R³ and R⁴ are independently selected from C₁₋₁₀alkyl,C₂₋₁₀alkenyl, C₂₋₁₀alkynyl, C₃₋₁₀cycloalkyl, heteroaryl and aryl, eachgroup being optionally substituted, orR¹ and R² are linked to form, together with the nitrogen atom to whichthey are attached, an optionally substituted monocyclic or polycyclic,saturated or unsaturated ring system that contains 3 to 30 carbon atoms,of which one or more of the carbon atoms is optionally replaced with aheteromoiety selected from O, S, NH and NC₁₋₆alkyl, and/orR³ and R⁴ are linked to form, together with the nitrogen atom to whichthey are attached, an optionally substituted monocyclic or polycyclic,saturated or unsaturated ring system that contains 3 to 30 carbon atoms,of which one or more of the carbon atoms is optionally replaced with aheteromoiety selected from O, S, NH and NC₁₋₆alkyl,the optional substituents on R¹, R², R³ and R⁴ are independentlyselected from one or more, optionally one to five, suitably one tothree, of C₁₋₆alkyl, halo, halo-substituted C₁₋₆alkyl, C₃₋₁₀cycloalkyl,aryl and heteroaryl, andat least one of R¹, R², R³, R⁴, the ring system formed by R¹ and R² andthe ring system formed by R³ and R⁴, or a substituent thereon, comprisesat least one chiral center; andY is a non-coordinating counter anion.

In an embodiment of the disclosure R¹, R², R³ and R⁴ in the formamidiumsalts of formula III are independently selected from C₁₋₆alkyl,C₅₋₆cycloalkyl and aryl, each group being optionally substituted, or R¹and R² and/or R³ and R⁴ are linked to form, together with the nitrogenatom to which they are attached, an optionally substituted monocyclic,saturated ring system that contains 4 to 7 carbon atoms, and theoptional substituents on R¹, R², R³ and R⁴ are independently selectedfrom one or more, optionally one to five, suitably one to three, ofC₁₋₄alkyl, halo-substituted C₁₋₄alkyl, C₅₋₆cycloalkyl and aryl, and atleast one of R¹, R², R³, R⁴, the ring system formed by R¹ and R² and thering system formed by R³ and R⁴, or a substituent thereon, comprises atleast one chiral center.

In a further embodiment of the disclosure, Y is any non-coordinatingcounter anion, including, for example, BF₄ ⁻ or B(C₆F₅)₄.

In an embodiment of the disclosure, the formamidium salt of formula(III) is selected from:

where Y is a counteranion, and analogs of the above compounds that aresubstituted on the alkyl groups, phenyl rings, aromatic and/orpyrrolidine rings with one or more substituents independently selectedfrom C₁₋₆alkyl, halo, halo-substituted C₁₋₆alkyl, OC₁₋₆alkyl andhalo-substituted OC₁₋₆alkyl.

The formamidium salts of formula III may be prepared, for example, byreacting an aldehyde of formula IV with an amine of the formula V underVilsmeier Haack reaction conditions, for example in the presence ofPOCl₃, or equivalent reagent, at reduced temperatures (e.g. about 10° C.to −90° C.) in an inert anhydrous solvent.

wherein R¹, R², R³ and R⁴ are as defined in formula III. Suitably thePOCl₃, or equivalent reagent, is added to the compound of formula IV atabout −50° C. to about −90° C., followed by warming to room temperaturefor a time sufficient to form the intermediate iminium salt and theresulting mixture is cooled to about 5° C. to about −5° C. and the amineof formula V is added. A person skilled in the art would appreciate thatthe reaction times and temperatures can be varied, depending on theidentity of the compounds of formula IV and V, to optimize the yield ofthe compounds of formula III. The compounds of formula IV and V areeither commercially available or may be prepared using methods known inthe art, for example as described herein below.

(III) Methods of the Disclosure

The present disclosure also includes a method of performingmetal-catalyzed organic synthesis reactions comprising contactingsubstrates for the organic synthesis reaction with a metal catalyst ofthe formula I as defined above under conditions for performing theorganic synthesis reaction, and optionally isolating one or moreproducts from the organic synthesis reaction. In an embodiment of thedisclosure, the organic synthesis reaction is any reaction the benefitsfrom the presence or use of a metal catalyst, for example, but notlimited to, hydrosilations, hydrogenations, conjugate additions andcross-couplings (for example Suzuki, Sonogashira and Heck reactions). Inan embodiment of the disclosure, the organic synthesis transformation isan asymmetric or chiral synthesis reaction (i.e. provides one enantiomerin excess of the other).

In an embodiment of the disclosure, the catalyst of formula I isgenerated in situ in solution and the resulting catalyst solution isadded to the appropriate starting materials for the organic synthesistransformation.

The following non-limiting examples are illustrative of the presentdisclosure:

(IV) Examples Materials and Methods

All reactions were carried out under nitrogen atmosphere; solvents weredried using standard techniques. All secondary amines and secondaryformamides were obtained from Sigma Aldrich and were used as receivedexcept R,R-2,5-diphenylpyrrolidine andR,R—N-formyl-2,5-diphenylpyrrolidine which were synthesized according tothe reported procedures.⁹⁻¹¹

Example 1 General Procedure to Synthesize Formamidinium Salts

The formamidinium salts were synthesized through Vilsmeier-Haackchemistry according to a modified procedure reported by Alder et al.¹²To a solution of an appropriate secondary formamide in drydichloromethane was added one equivalent of POCl₃ at −78° C. and themixture was allowed to warm to room temperature and stirred for twohours. The mixture was cooled to 0° C. and a solution of one equivalentof an appropriate secondary amine and one equivalent of triethylamine indichloromethane was added, it was again allowed to warm to roomtemperature and stirred for two hours. The solvent was removed in vacuo,the crude product was dissolved in CH₂Cl₂ and washed extensively withsaturated aqueous NaBF₄. The organic layer was separated, dried (MgSO₄),filtered and evaporated in vacuo. The crude product was the purified bycolumn chromatography [silica gel, MeOH/CH₂Cl₂ (1:10)].

(a)(R,R,R,R)-2,5-diphenylpyrrolidin-1-ylmethylene(2,5-diphenylpyrrolidinium)tetrafluoroborate (compound IIIj) &(S,S,S,S)-2,5-diphenylpyrrolidin-1-ylmethylene(2,5-diphenylpyrrolidinium)tetrafluoroborate(compound IIIk)

These compounds were prepared from(R,R)—N-formyl-2,5-diphenylpyrrolidine or(S,S)—N-formyl-2,5-diphenylpyrrolidine and (R,R)-2,5-diphenylpyrrolidineor (S,S)-2,5-diphenylpyrrolidine to give a low melting yellow solid in78-80% yield. ¹H NMR [CDCl₃, 500 MHz] δ: 9.67 (s, 1H), 7.44-7.37 (m,6H), 7,20-7.13 (m, 10H) 6.78-6.76 (m, 4H), 5.92-5.90 (m, 2H), 4.95-4.93(m, 2H), 2.34-2.20 (m, 4H), 1.68-1.60 (m, 2H); ¹³C NMR [CDCl₃, 75 MHz]δ: 155.81, 140.95, 140.88, 130.17, 129.08, 128.96, 128.30, 126.33,124.89, 70.88, 64.63, 33.59, 29.65.

(b)(R,R,R,R)-2,5-dimethylpyrrolidin-1-ylmethylene(2,5-dimethylpyrrolidinium)tetrafluoroborate (compound IIIf) &(S,S,S,S)-2,5-dimethylpyrrolidin-1-ylmethylene(2,5-dimethylpyrrolidinium)tetrafluoroborate(compound IIIg)

These compounds were prepared from(R,R)—N-formyl-2,5-dimethylpyrrolidine or(S,S)—N-formyl-2,5-dimethylpyrrolidine and (R,R)-2,5-dimethylpyrrolidineor (R,R)-2,5-dimethylpyrrolidine to give a low melting yellow solid in60-65% yield. ¹H NMR [CDCl₃, 500 MHz] δ: 8.10 (s, 1H), 4.40-4.20 (m,4H), 2.20-1.80 (m, 6H), 1.80-1.60 (m, 2H), 1.55 (6H, d, J=7.5 Hz), 1.50(6H, d, J=7.5 Hz).

(c)(R,R,R,R)-2,5-diethylpyrrolidin-1-ylmethylene(2,5-diethylpyrrolidinium)tetrafluoroborate (compound IIIh) &(S,S,S,S)-2,5-diethylpyrrolidin-1-ylmethylene(2,5-diethylpyrrolidinium)tetrafluoroborate (compound IIIi)

These compounds were prepared from (R,R)—N-formyl-2,5-diethylpyrrolidineor (S,S)—N-formyl-2,5-diethylpyrrolidine and(R,R)-2,5-diethylpyrrolidine or (R,R)-2,5-diethylpyrrolidine to give alow melting yellow solid in 60-65% yield. ¹H NMR [CDCl₃, 500 MHz] δ:7.95 (s, 1H), 4.40-4.20 (m, 4H), 2.21-1.70 (m, 8H), 1.68 (4H, q, J=7.5Hz), 1.63 (4H, t, J=7.5 Hz), 1.35 (6H, d, J=7.5 Hz), 1.30 (6H, d, J=7.5Hz).

(c)(2S,5S)-1-(((2S,5S)-2,5-di(naphthalen-1-yl)pyrrolidin-1-yl)methylene)-2,5-di(naphthalen-1-yl)pyrrolidiniumtetrafluoroborate (compound IIIl) &(2R,5R)-1-(((2R,5R)-2,5-di(naphthalen-1-yl)pyrrolidin-1-yl)methylene)-2,5-di(naphthalen-1-yl)pyrrolidiniumtetrafluoroborate (compound IIIm)

These compounds were prepared from(2S,5S)-2,5-di(naphthalen-1-yl)pyrrolidine-1-carbaldehyde or(2R,5R)-2,5-di(naphthalen-1-yl)pyrrolidine-1-carbaldehyde and(2S,5S)-2,5-di(naphthalen-1-yl)pyrrolidine or(2R,5R)-2,5-di(naphthalen-1-yl)pyrrolidine to give a yellow-brown solidin 40-50% yield.

(b) (R,R)-2,5-diphenylpyrrolidin-1-ylmethylene-(N,N-dimethylammonium)tetrafluoroborate (compound IIIa)

This compound was prepared from N,N-dimethyl formamide and(R,R)-2,5-diphenylpyrrolidine to give a low melting point clear yellowsolid in 95% yield. ¹H NMR [CDCl₃, 300 MHz] δ: 8.43 (s, 1H), 7.39-7.19(m, 10H), 5.99-5.97 (m, 2H), 3.12 (s, 3H), 2.93 (s, 3), 2.71-2.69 (m,1H), 2.34-3.32 (m, 1H), 1.89-1.86 (m, 2H). ¹³C NMR [CDCl₃, 75 MHz] δ:156.32, 141.28, 140.75, 129.66, 129.21, 128.30, 126.77, 125.10, 69.89,64.54, 46.36, 39.02, 34.82, 30.10.

(c) (R,R)—(N,N-diphenylamino)-N-ylmethylene(2,5-diphenylpyrrolidinium)tetrafluoroborate (compound IIIb)

This compound was prepared from (R,R)—N-formyl-2,5-diphenylpyrrolidineand diphenyl amine, and a low melting point dark brown solid wasobtained in 96% yield. ¹H NMR [CDCl₃, 500 MHz] δ: 9.08 (s, 1H),7.60-7.55 (m, 5H), 7.44-7.39 (m, 3H), 7.33-7.31 (m, 4H), 7.26-7.23 (m,4H), 7.17-7.16 (m, 3H), 6.95-6.93 (m, 1H), 5.92-5.90 (d, 1H), 4.62-4.59(m, 1H), 2.62-2.54 (m, 2H), 2.06-1.96 (m, 2H). ¹³C NMR [CDCl₃, 75 MHz]δ: 153.14, 143.23, 140.78, 138.52, 137.87, 129.97, 129.86, 129.72,129.46, 129.38, 129.11, 128.94, 128.79, 128.04, 127.52, 126.57, 125,15,124.45, 71.57, 67.42, 36.08, 32.01.

(d) (R,R)—(N,N-di-p-tolylamino)-N-ylmethylene(2,5-diphenylpyrrolidinium)tetrafluoroborate (compound IIIc)

This compound was prepared from (R,R)—N-formyl-2,5-diphenylpyrrolidineand di-p-tolyl amine, and a low melting point dark red solid wasobtained in 97% yield. ¹H NMR [CDCl₃, 300 MHz] d: 8.13 (s, 1H),7.63-7.53 (m, 2H), 7.53-7.42 (m, 3H), 7.36-7.28 (m, 3H), 7.22-7.16 (m,3H), 7.03-6.93 (m, 5H), 6.68-6.66 (m, 1H), 6.08-6.04 (m, 1H), 5.78-5.75(m, 1H), 4.92-4.87 (m, 1H), 2.70-2.63 (m, 1H), 2.54-2.47 (m, 1H), 2.39(s, 3H), 2.19 (s, 3H), 1.97-1.90 (m, 1H). ¹³C NMR [CDCl₃, 75 MHz] d:152.30, 141.05, 140.61, 139.80, 139.15, 138.60, 135.40, 130.48, 129.80,129.71, 129.06, 127.99, 127.63, 127.11, 126.38, 125.01, 124.07, 121.71,71.85, 67.30, 36.14, 32.28, 21.30, 20.92.

(e) (R,R)-2,5-diphenylpyrrolidin-1-ylmethylenepyrrolidiniumtetrafluoroborate (compound IIId)

This compound was prepared from N-formyl pyrrolidine and(R,R)-2,5-diphenylpyrrolidine to form a clear yellow low melting pointsolid in 82% yield. ¹H NMR [CDCl₃, 500 MHz] δ: 9.00 (s, 1H), 7.46-7.31(m, 10H), 6.04-6.03 (d, 1H), 5.82-5.80 (d, 1H), 4.03-4.01 (m, 1H),3.85-3.83 (m, 1H), 3.63-3.61 (m, 1H), 3.05-3.03 (m, 1H), 2.76-2.74 (m,1H), 2.44-2.42 (m, 1H), 1.98-1.65 (m, 6H). ¹³C NMR [CDCl₃, 75 MHz] δ:152.94, 141.25, 140.93, 129.82, 129.49, 128.63, 128.34, 127.00, 124.89,69.52, 64.26, 55.40, 48.42, 34.41, 30.44, 25.87, 23.69.

(f) (R,R)-2,5-diphenylpyrrolidin-1-ylmethylenepiperidiniumtetrafluoroborate (compound IIIe)

This compound was prepared from N-formyl piperidine and(R,R)-2,5-diphenylpyrrolidine to form a clear yellow low melting pointsolid in 93% yield. ¹H NMR [CDCl₃, 300 MHz] δ 8.97 (s, 1H), 7.47-7.27(m, 10H), 6.22-6.20 (d, 1H), 5.59-5.56 (d, 1H), 3.78-3.74 (m, 1H),3.54-3.42 (m, 2H), 3.33-3.29 (m, 1H), 2.57-2.54 (m, 1H), 2.30-2.28 (m,1H), 2.02-1.99 (m, 2H), 1.65-1.61 (m, 2H), 1.42-1.40 (m, 2H), 1.24-1.19(m, 1H), 0.54-0.50 (m, 1H). ¹³C NMR [CDCl₃, 75 MHz] δ: 153.61, 141.31,139.41, 129.61, 129.16, 128.35, 128.23, 126.66, 125.65, 70.29, 64.85,56.04, 48.64, 35.15, 30.20, 26.09, 24.73, 22.84.

Example 2 General Procedure for the Hydrosilylation of Ketones (a)Synthesis of Chiral Rhodium Catalyst

To a solution of the chiral acyclic diaminocarbene (ADC) formamidiumsalt (IIIj, 1.00 mmol) in THF (2 mL) at −78° C. was added a solution ofLDA (2.0 M in THF, 1.1 mmol) dropwise. The solution was allowed to stirfor 30 min at −78° C., 30 min at 0° C. and then recooled to −78° C. Asolution of [Rh(COD)Cl]₂ (0.45 mmol) in THF (1 mL) was then addeddropwise, and the reaction mixture was allowed to stir for 1 h whilewarming to rt. The chiral rhodium ADC complex (Ia) was generated insitu.

(b) Enantioselective Hydrosilylation of Ketones Using a Chiral RhodiumADC Catalyst

In another flask was added the aryl ketone (1.00 mmol) and PhSiH₂ (1.50mmol) and THF (4 mL). A solution of the Rh-carbene complex prepared inExample 2(a) (0.25 M in THF, 0.02 mmol) was the added. The reactionmixture was stirred for 24 h at rt. The reaction mixture was thenquenched with the addition of water (1.5 mL) and 0.5N HCl (0.5 mL). Theresulting mixture was stirred for another hour at rt. The organiccomponents were then extracted with Et₂O (5×10 mL). The organic extractswere then dried (MgSO₄), filtered and concentrated in vacuo to afford aclear, colourless oil. The residue was purified by column chromatography(silica gel, EtOAc/hexanes) to provide the chiral secondary alcohols.The enantioselectivities were assayed by chiral HPLC. The yields andee's are shown above.

Example 3 Enantioselective Conjugate Addition Using a Chiral Copper ADCCatalyst

To a solution of the chiral acyclic diaminocarbene (ADC) formamidiumsalt (IIIj, 1.00 mmol) in THF (2 mL) at −78° C. was added a solution ofLDA (2.0 M in THF, 1.1 mmol) dropwise. The solution was allowed to stirfor 30 min at −78° C., 30 min at 0° C. and then recooled to −78° C. Asolution of Cu(OTf)₂ (1.00 mmol) in THF (1 mL) was then added dropwise,and the reaction mixture was allowed to stir for 1 h while warming tort. The presumed chiral copper ADC complex was thus generated in situ.

In another flask was added the enone (1.00 mmol) and Et₂O (3.00 mL). Themixture was cooled to −40° C. The chiral copper-ADC complex preparedabove was then added (0.25 M, 0.06 mmol). The mixture was stirred for 15min and then Et₂Zn was added (3 mmol). The resulting reaction mixturewas stirred for 8 h at −40° C. The reaction mixture was then quenchedwith the addition of water (1.5 mL) and 0.5N HCl (0.5 mL). The resultingmixture was stirred for another hour at rt. The organic components werethen extracted with Et₂O (5×10 mL). The organic extracts were then dried(MgSO₄), filtered and concentrated in vacuo to afford a yellow oil. Theresidue was purified by column chromatography (silica gel,EtOAc/hexanes) to provide the chiral secondary alcohols. Theenantioselectivity was assayed by chiral HPLC. The yields and ee's areshown in the equation above.

While the present invention has been described with reference to whatare presently considered to be the preferred examples, it is to beunderstood that the invention is not limited to the disclosed examples.To the contrary, the invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

All publications, patents and patent applications are hereinincorporated by reference in their entirety to the same extent as ifeach individual publication, patent or patent application wasspecifically and individually indicated to be incorporated by referencein its entirety. Where a term in the present application is found to bedefined differently in a document incorporated herein by reference, thedefinition provided herein is to serve as the definition for the term.

FULL CITATION FOR DOCUMENTS REFERRED TO IN THE SPECIFICATION

-   1. (a) Thayer, A. M Chem. Eng. News 2007, 85, Issue 32, 11. (b)    Comprehensive Asymmetric Catalysis, Jacosen, E. N., Pfaltz, A.,    Yamamoto, H., Eds.; Springer-Verlag: Berlin, Vol. 1-3, 1999.-   2. Tsuji, J. Transition Metal Reagens and Catalysts; Wiley: West    Sussex, England, 2002.-   3. For recent reviews, see: (a) Kantchev, E. A. B.; O'Brien, C. J.;    Organ, M. G. Angew Chem., Int. Ed. 2007, 46, 2768. (b) Tekavec, T.    N.; Louie, J. Top. Organomet. Chem. 2007, 21, 159.-   4. Cavallo, L.; Correa A.; Costabile, C; Jacobsen, H. J. Organomet.    Chem. 2005, 690, 5407.-   5. (a) Gillingham D. G.; Hoveyda, A. H. Angew. Chem., Int. Ed. 2007,    46, 3860. (b) Martin, D.; Kehrli, S.; d'Augustin, M.; Clavier, H.;    Mauduit, M.; Alexakis, A. J. Am. Chem. Soc. 2006, 128, 8416. (c) For    a recent review, see: Roland, S.; Mangeney, P. Top. Organomet. Chem.    2005, 15, 191.-   6. For the first isolation of an ADC, see: Alder, R. W.; Allen, P.    R.; Murray, M.; Orpen, A. G. Angew. Chem., Int. Ed. 1996, 35, 1121.-   7. For recent reports on ADC, see: (a) Frey, G. D.; Herdtweck, E.;    Herrmann, W. A. J. Organomet. Chem. 2006, 691, 2465. (b)    Herrmann, W. A.; Schütz.; Frey, G. D.; Herdtweck, E. Organometallics    2006, 25, 2437. (c) Kremzow, D.; Seidel, G.; Lehmann, C. W.;    Fürstner, A. Chem. Eur. J. 2005, 11, 1833.-   8. Dhudshia, B.; Thadani, A. N. Chem. Commun. 2006, 668.-   9. Michael Chong, J.; Clarke, I. S.; Koch, I.; Olbach, P. C.;    Taylor, N. J. Tetrahedron: Asymmetry 1995, 6, 409-418.-   10. Iseki, K.; Mizuno, S.; Kuroki, Y.; Kobayashi, Y. Tetrahedron    1999, 55, 977-988.-   11. Krimen, L. I. Org Synth 1970, 50, 1-3.-   12. Alder, R. W.; Blake, M. E.; Bufali, S.; Butts, C. P.; Orpen, A.    G.; Schutz, J.; Williams, S. J. J. Chem. Soc., Perkin Trans. 12001,    1586-1593.

1. A metal catalyst of the formula I:M[ADC][X]_(n)  (I) wherein M is a metal; ADC is a chiral acyclic carbeneof the formula II:

R¹, R², R³ and R⁴ are independently selected from C₁₋₁₀alkyl,C₂₋₁₀alkenyl, C₂₋₁₀alkynyl, C₃₋₁₀cycloalkyl, heteroaryl and aryl, eachgroup being optionally substituted, or R¹ and R² are linked to form,together with the nitrogen atom to which they are attached, anoptionally substituted monocyclic or polycyclic, saturated orunsaturated ring system that contains 3 to 30 carbon atoms, of which oneor more of the carbon atoms is optionally replaced with a heteromoietyselected from O, S, NH and NC₁₋₆alkyl, and/or R³ and R⁴ are linked toform, together with the nitrogen atom to which they are attached, anoptionally substituted monocyclic or polycyclic, saturated orunsaturated ring system that contains 3 to 30 carbon atoms, of which oneor more of the carbon atoms is optionally replaced with a heteromoietyselected from O, S, NH and NC₁₋₆alkyl, the optional substituents R¹, R²,R³ and R⁴ on are independently selected from one or more of C₁₋₆alkyl,halo, halo-substituted C₁₋₆alkyl, OC₁₋₆alkyl, halo-substitutedOC₁₋₆alkyl, C₃₋₁₀cycloalkyl, aryl and heteroaryl, and at least one ofR¹, R², R³, R⁴, the ring system formed by R¹ and R² and the ring systemformed by R³ and R⁴, or a substituent thereon, comprises at least onechiral center; X is a neutral or an anionic ligand; and n is an integerrepresenting the number of ligands, X, to fulfill the valencyrequirements of N, and when x is greater than 1, each X may be the sameor different.
 2. The metal catalyst according to claim 1, wherein R¹,R², R³ and R⁴ are independently selected from C₁₋₆alkyl, C₅₋₆cycloalkyland aryl, each group being optionally substituted, or R¹ and R² and/orR³ and R⁴ are linked to form, together with the nitrogen atom to whichthey are attached, an optionally substituted monocyclic, saturated ringsystem that contains 4 to 7 carbon atoms, and the optional substituentson R¹, R², R³ and R⁴ are independently selected from one to five ofC₁₋₄alkyl, halo-substituted C₁₋₄alkyl, C₅₋₆cycloalkyl and aryl, and atleast one of R¹, R², R³, R⁴, the ring system formed by R¹ and R² and thering system formed by R³ and R⁴, or a substituent thereon, comprises atleast one chiral center.
 3. The metal catalyst according to claim 2,wherein the chiral ADC of formula II is selected from:

and analogs of the above compounds that are substituted on the alkylrings, phenyl rings, aromatic and/or pyrrolidine rings with one or moresubstituents independently selected from C₁₋₆alkyl, halo,halo-substituted C₁₋₆alkyl, OC₁₋₆alkyl and halo-substituted OC₁₋₆alkyl.4. The metal catalyst according to claim 1, wherein M is any transitionmetal, or other metal selected from B, Al, Ga, Ge, In, Sn, Sb, TI, Pb,Bi and Po, or a lanthanide or actinide.
 5. The metal catalyst accordingto claim 4, wherein M is selected from Cu, Ag, Au, Sn, Ni, Pd, Pt, Co,Rh, Ir, Fe, Ru, Os and Re.
 6. The metal catalyst according to claim 1,wherein X is selected from any ancillary ligand, including phosphine,amine, alkene, diamine, diphosphine, aminophosphine, halo, HO⁻, R⁵O⁻ andR⁵C(O)O⁻, wherein R⁵ is H or C₁₋₆alkyl.
 7. The metal catalyst accordingto claim 6, wherein X is chloro.
 8. The metal catalyst according toclaim 1, wherein when n is greater than 1, all X ligands are the same.9. A chiral formamidium salt of the formula III:

wherein R¹, R², R³ and R⁴ are independently selected from C₁₋₁₀alkyl,C₂₋₁₀alkenyl, C₂₋₁₀alkynyl, C₃₋₁₀cycloalkyl, heteroaryl and aryl, eachgroup being optionally substituted, or R¹ and R² are linked to form,together with the nitrogen atom to which they are attached, anoptionally substituted monocyclic or polycyclic, saturated orunsaturated ring system that contains 3 to 30 carbon atoms, of which oneor more of the carbon atoms is optionally replaced with a heteromoietyselected from O, S, NH and NC₁₋₆alkyl, and/or R³ and R⁴ are linked toform, together with the nitrogen atom to which they are attached, anoptionally substituted monocyclic or polycyclic, saturated orunsaturated ring system that contains 3 to 30 carbon atoms, of which oneor more of the carbon atoms is optionally replaced with a heteromoietyselected from O, S, NH and NC₁₋₆alkyl, the optional substituents on R¹,R², R³ and R⁴ are independently selected from one or more of C₁₋₆alkyl,halo, halo-substituted C₁₋₆alkyl, C₃₋₁₀cycloalkyl, aryl and heteroaryl,and at least one of R¹, R², R³, R⁴, the ring system formed by R¹ and R²and the ring system formed by R³ and R⁴, or a substituent thereon,comprises at least one chiral center; and Y is a non-coordinatingcounter anion.
 10. The chiral formamidium salt of claim 9, wherein R¹,R², R³ and R⁴ are independently selected from C₁₋₆alkyl, C₅₋₆cycloalkyland aryl, each group being optionally substituted, or R¹ and R² and/orR³ and R⁴ are linked to form, together with the nitrogen atom to whichthey are attached, an optionally substituted monocyclic, saturated ringsystem that contains 4 to 7 carbon atoms, and the optional substituentson R¹, R², R³ and R⁴ are independently selected from one to five ofC₁₋₄alkyl, halo-substituted C₁₋₄alkyl, C₅₋₆cycloalkyl and aryl, and atleast one of R¹, R², R³, R⁴, the ring system formed by R¹ and R² and thering system formed by R³ and R⁴, or a substituent thereon, comprises atleast one chiral center.
 11. The chiral formamidium salt of claim 9,wherein Y is BF₄ ⁻ or B(C₆F₅)₄.
 12. The chiral formamidium salt of claim9 selected from:

where Y is a counteranion, and analogs of the above compounds that aresubstituted on the alkyl groups, phenyl rings, aromatic and/orpyrrolidine rings with one or more substituents independently selectedfrom C₁₋₆alkyl, halo and halo-substituted C₁₋₆alkyl.
 13. A method ofperforming metal-catalyzed organic synthesis reactions comprisingcontacting substrates for the organic synthesis reaction with a metalcatalyst of the formula I as defined in claim 1 under conditions forperforming the organic synthesis reaction, and optionally isolating oneor more products from the organic synthesis reaction.
 14. The methodaccording to claim 13, wherein the organic synthesis reaction isselected from hydrosilations, hydrogenations, conjugate additions andcross-couplings.
 15. The method according to claim 13, wherein theorganic synthesis transformation is an asymmetric or chiral synthesisreaction.